Yamaha HS8 Repair - Capacitor Alternatives

[GlassMonolith]

Hi, all. I'm trying to figure out what I can use as alternative to the two large 4700uf/50v capacitors on my HS8. I'm on Digikey and I have a couple results in front of me (the Chemi-Con specifically are all obsolete or "special order", so I'm unable to order those) and I was hoping to figure out which caps were possible alternatives.

The things I'm tripping over are;
1: ESR. Can I go lower or higher than stock?
2: Ripple Current. Lower or higher?

I'm also realizing I may not have a 100% lead on what this stock cap actually IS.

Any help is incredibly appreciated.

 

[Ike Zimbel]

You can't go wrong with Panasonic or Nichicon. Any of their caps that match the specs on these will work. Lower ESR can't hurt, ditto higher ripple current. Those caps are most likely power supply filter caps...I assume you are replacing them because they are showing some physical signs of needing replacement?

 

[GlassMonolith]

You can't go wrong with Panasonic or Nichicon. Any of their caps that match the specs on these will work. Lower ESR can't hurt, ditto higher ripple current. Those caps are most likely power supply filter caps...I assume you are replacing them because they are showing some physical signs of needing replacement?

Replacing after a power surge that took out one of the speakers. Killed the fuse in the separate power-circuit. New fuse in and the powerAMP cap(s) started smoking and immediately lost the new fuse again. Working on metering the powerAMP atm, but transformer and power-circuit both appeared to work fine when swapping to my working speaker.

Atm all I have metered are these two large caps, and they're testing at 3.89mohm & 1.55kohm.

 

[Brian Roth]

FWIW....if the caps are actually smoking, be sure to check the rectifier diodes. One or more might be shorted.

Bri

 

[GlassMonolith]

FWIW....if the caps are actually smoking, be sure to check the rectifier diodes. One or more might be shorted.

Bri

Not quite sure what to look for with those. Just cross ref. on googleimages for "rectifier diodes" and I only see two "ferrite beads" on the AC-circuit, but nothing similar on the poweramp board.

I do have what looks like a regulator with 4 legs the schematics list as "Diode stack". Would that be it?

 

[dmp]

It's a diode bridge in the HS8, part D401
You could test it with a multimeter with a diode function, or just replace it:
https://www.digikey.com/en/products/detail/micro-commercial-co/RS403GL-BP/2233900

For the caps, match the 4700uF and 50v, then match the lead spacing (measure on the pcb) and make sure the diameter and length will fit.
THEN - at your discretion get the highest temperature rating (105C) and lifecycle hours (1000 to 5000) you want to pay for. This is the durability of the part.
I wouldn't worry about any other spec for a power filtering cap like this.

You might want to check the 33 ohm resistors that follow the caps too

 

[GlassMonolith]

It's a diode bridge in the HS8, part D401
You could test it with a multimeter with a diode function, or just replace it:
https://www.digikey.com/en/products/detail/micro-commercial-co/RS403GL-BP/2233900

For the caps, match the 4700uF and 50v, then match the lead spacing (measure on the pcb) and make sure the diameter and length will fit.
THEN - at your discretion get the highest temperature rating (105C) and lifecycle hours (1000 to 5000) you want to pay for. This is the durability of the part.
I wouldn't worry about any other spec for a power filtering cap like this.

You might want to check the 33 ohm resistors that follow the caps too

Awesome. Thanks so much for this info. The only additional question I think I have at the moment is; Ripple Current and ESR. How can I find out what the original spec was so I know which way to go with them, or are they also not important in this respect?

 

[dmp]

Not important.